Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. In one variation of such devices, a belt is placed around the patient's chest and the belt is used to effect chest compressions, for example our commercial device, sold under the trademark AUTOPULSE®. Our own patents, Mollenauer, et al., Resuscitation Device Having A Motor Driven Belt To Constrict/Compress The Chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Sherman, et al., CPR Assist Device with Pressure Bladder Feedback, U.S. Pat. No. 6,616,620 (Sep. 9, 2003); Sherman, et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman, et al., Modular CPR assist device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002); Jensen, Lightweight Electro-Mechanical Chest Compression Device, U.S. Pat. No. 7,347,832 (Mar. 25, 2008) and Quintana, et al., Methods and Devices for Attaching a Belt Cartridge to a Chest Compression Device, U.S. Pat. No. 7,354,407 (Apr. 8, 2008), show chest compression devices that compress a patient's chest with a belt. Each of these patents is hereby incorporated by reference in their entirety.
These devices have proven to be valuable alternatives to manual CPR, and evidence is mounting that they provide circulation superior to that provided by manual CPR, and also result in higher survival rates for cardiac arrest victims. The devices provide Chest compressions at resuscitative rates and depths. A resuscitative rate may be any rate of compressions considered effective to induce blood flow in a cardiac arrest victim, typically 60 to 120 compressions per minute (the CPR Guidelines 2010 recommends 80 to 100 compression per minute), and a resuscitative depth may be any depth considered effective to induce blood flow, and typically 1.5 to 2.5 inches (the CPR Guidelines 2010 recommends about 2 inches per compression).
The AUTOPULSE® chest compression device uses a belt, which is releasably attached to a drive spool with the housing of the device. In a convenient arrangement, a spline is secured to the belt, and the spline fits into a slot in the drive spool of the device. The drive spool is accessible from the bottom, or posterior aspect, of the device. Before use, a fresh belt is fitted to the device, and this requires lifting the device to insert the spline into the drive spool. The patient is then placed on the housing of the device, and the belt is secured over the chest of the patient. Opposite ends of the belt are held together, over the chest of the patient, with hook and loop fasteners. The arrangement has proven effective for treating cardiac arrest victims and convenient to use. Other belt-based CPR compressions devices have been proposed, but not implemented in clinical use. Lach, Resuscitation Method and Apparatus, U.S. Pat. No. 4,770,164 (Sep. 13, 1988) secures a belt around a patient by threading it under a first roller, then under a second roller, over the patient, back under the first roller, and then to a large roller disposed on one side of the patient. The belt is secured to the roller with hook and loop fasteners, and is sized to the patient by the operator of the device. Kelly, Chest Compression Apparatus for Cardiac Arrest, U.S. Pat. No. 5,738,637 (Apr. 14, 1998) uses a belt that is bolted at its midpoint to the underside of a backboard, than secured to a scissor-mechanism on the patient's chest with hook and loop fasteners. Belt installation is not convenient in either device. A new, more convenient arrangement of the drive components and belt is disclosed in this application.
Another feature of our AUTOPULSE® CPR chest compression device is the ability of the control system to hold the compression belt at the height of compression. The AUTOPULSE® can operate to perform compression in repeated compression cycles comprising a compression stroke, a high compression hold, a release period, and an inter-compression hold. No other automated CPR chest compression device is capable of holding compressions at a high threshold of compression. The method of operating the AUTOPULSE® device to accomplish compressions in cycles of compression, hold, and release is covered by our previous patent, Sherman, et al., Modular CPR assist device to hold at a threshold of tightness, U.S. Pat. No. 7,374,548 (May 20, 2008). The holding periods are accomplished with a brake operably connected to the motor drive shaft of the device, which can be energized to stop the drive shaft to lock the belt in place about the patient. A new, more energy-efficient braking system is disclosed in this application.
On occasion, a chest compression device must be used on a patient at the same time that doctors want to take x-rays of the patient's chest. This is not possible if the radiopaque metal components of the chest compression device (the motor and drive train) are located directly under the load distributing portion of the compression belt, which overlies the patient's chest and heart when properly installed, so that the radiopaque component are also located under the heart. This means that radiopaque component are in the field of view of the x-ray machine.